Note: Descriptions are shown in the official language in which they were submitted.
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DESCRIPTION
GENERATOR-MOTOR FOR INTERNAL COMBUSTION ENGINE
Technical Field
This invention relates to a generator-motor for
internal combustion engines, which operates not only as a
generator for converting energy of rotation of an internal
combustion engine into electric energy, but also as a motor
for generating such a torque as to assist or suppress the
torque on the internal combustion engine .
1 0 Background Art
A typical generatorfor internal combustion engines
mounted on vehicles or ships includes an alternator (ACG)
with its rotating shaft mechanically coupled to a crank
shaft of an internal combustion engine (generally, through
1 5 an alternator belt) ; a rectifier for converting AC power
into DC power, the AC power generated by the alternator
according to the rotating speed of the internal combustion
engine; and a regulator for controlling the voltage level
of the DC power according to the voltage across a battery.
2 o Fig. 2 is a schematic diagram showing a structure of
a conventional alternator 50, in which a DC field coil 53 is
wound around a rotor 52 integrally formed with the rotating
shaft and a three-phase coil 55 is wound around a stator 54.
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In the condition that the DC field coil 53 is excited by
supplying direct current from the battery (not shown) , the
rotor 52 is rotated to create an alternative magnetic
field. Consequently, the three-phase coil 55 of the stator
54 generates AC power with a frequency corresponding to the
rotation speed of the rotor 52. In some cases, the rotor 52
may be provided with a permanent magnet instead of the DC
field coil 53.
With such an internal combustion engine for vehicles
1 0 or the like, since the rotor 52 of the alternator 50 is
mechanically coupled to the crank shaft of the internal
combustion engine even when the battery is fully charged
and power generation is no longer necessary, the rotor 52 is
rotated constantly to cause rotation loss due to belt
1 5 driving torque or cooling fan resistance.
Disclosure of Invention
The present invention has been made by taking into
account that such a conventional alternator is a generator
with a construction of synchronous motor type, and an
2 0 object thereof is to provide a generator-motor for internal
combustion engines, which operates not only as a generator
but also as a motor without any distinct change in structure
of the conventional alternator.
The present invention is characterized in that the
2 5 generator-motor for internal combustion engines comprising
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an alternator which includes a stator having multi-phase
windings and a rotor having direct-current magnetic field
generation means, which rotor is mechanically coupled to a
rotating shaft of an internal combustion engine; output
control means converting an alternating current generated
in the multi-phase windings into direct current when said
alternator is in the generator mode, which alternating
current is induced by the rotation of said rotor resulting
from the rotation of the internal combustion engine;
l0 rotating magnetic field generation means generating
alternating current to be supplied to the mufti-phase
windings for generating a rotating magnetic field which
causes said alternator to operate in the motor mode;
switching means for selectively connecting the mufti-phase
1 5 windings of said stator to either said output control means
or said rotating magnetic field generation means .
The rotating magnetic field generation means of the
present invention is actuated according to the operating
condition of the internal combustion engine in the
20 following manners.
(1) The rotating magnetic field generation means
generates a rotating magnetic field which causes the
alternator (in the motor mode) to produce a torque
assisting or suppressing the rotation of the internal
2 5 combustion engine so that fluctuations in rotation of the
internal combustion engine is absorbed and a deviation of
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the engine rotation with respect to a target value
decreases at the time of idling or the like .
(2) The rotating magnetic field generation means
generates in the stator such a rotating magnetic field as to
cause the alternator (in the motor mode) to produce a torque
assisting the rotation of the internal combustion engine
when:
(a) power generation is no longer necessary;
(b) the internal combustion engine is started; and
1 0 (c) the vehicle or the like with the internal
combustion engine mounted thereon is in an acceleration
condition.
(3) The rotating magnetic field generation means
generates in the stator such a rotating magnetic field as to
1 5 cause the alternator (in the motor mode) to produce a torque
suppressing the rotation of the internal combustion engine
when:
(a) the vehicle or the like with the internal
combustion engine mounted thereon is in a braking
20 condition;
(b) driving wheels of the vehicle is in wheel spin
(slipping) condition;
(c) the rotating speed of the internal combustion
engine is likely to exceed an upper limit; and
2 5 (d) the vehicle speed is likely to exceed an upper limit.
According to the present invention, the generator of
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the internal combustion engine is capable of operating as a
motor without any distinct change in the structure so that
the rotation of the internal combustion engine is assisted
or suppressed according to the operating condition of the
internal combustion engine.
According to the feature ( 1 ) mentioned above,
fluctuations in the engine speed that likely happens at the
time of idling is prevented for stable operation of the
internal combustion engine.
1 0 The feature (2) makes it possible: (a) to cancel the
rotation loss due to the belt driving torque or cooling fan
resistance, and hence improve efficiency of the internal
combustion engine; (b) to assist the cel-motor (starting
motor) with the torque, and hence allow miniaturization of
1 5 the cel-motor, and quick and secure startup operation of
the internal combustion engine; and (c) to improve
acceleration performance of the engine.
The feature ( 3 ) makes it possible : ( a ) to improve
braking performance of the engine; (b) to carry out
2 0 traction control in improved response; (c) to prevent over
revolution of the internal combustion engine, and (d) to
improve its overspeed limitingfunction.
Brief Description of Drawings
Fig. 1 is a block diagram of a generator-motor for
2 5 vehicles according to an embodiment of the present
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invention;
Fig. 2 is a diagram showing the structure of the main
part of a conventional alternator;
Fig. 3 is a flowchart showing operation according to
the embodiment of the present invention;
Fig. 4 is a flowchart showing operation according to
another embodiment of the present invention;
Fig. 5 is a flowchart showing operation according to
still another embodiment of the present invention;
1 0 Fig. 6 is a flowchart showing operation according to
yet another embodiment of the present invention;
Fig. 7 is a flowchart showing operation according to
yet another embodiment of the present invention; and
Fig. 8 is a flowchart showing operation according to
1 5 yet another embodiment of the present invention.
Best Mode for Embodying the Invention
Referring to the drawings, the present invention
will be described below in detail. Fig. 1 is a block
diagram showing a generator-motorfor vehicles according to
2 0 an embodiment of the present invention, in which a vehicle
generator is designed to operate not only as a generator but
also as a motor. A rotor 1R of an alternator 1 is provided
with a DC magnetic field coil 11, and a stator 1S is provided
with a three-phase winding, or three-phase stator coils 12
2 5 ( 12a, 12b and 12c) . The rotor 1R is coupled to an engine
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crank shaft through a belt (both not shown) .
A DC magnetization control unit 2 supplies direct
current from a battery 9 to the DC magnetic field coil 11 to
cause the rotor 1R to generate a DC magnetic field. In a
generator mode, where the alternator 1 acts as a generator,
the alternator 1 may also supply a part of its output
current through the DC magnetization control unit 2 to the
rotor coil 11 for self-magnetization, as shown by a dotted
line 2A. An output controller 7 is provided with
1 0 conventional rectifier circuit 7a and regulator 7b for
regulating the output voltage, which is operative to
convert alternating current, that is induced in the
three-phase coils 12 of the stator 1S, into direct current
of a voltage corresponding to that across the battery 9.
1 5 An engine ECU 4 includes a rotating speed
measurement part 41, an acceleration judgment part 42, a
braking judgment part 43, a wheel spin detection part 44, a
vehicle speed measurement part 45 and a rotor phase-angle
detection part 46. The engine ECU 4 also includes other
2 0 functions for detecting an engine negative pressure Pb, a
throttle position B th, an electrical load a, and the like .
The rotor phase angle is detected, for example, by
arranging a Hall element 14 or a pick-up coil opposite to
the rotor 1R, or arranging a magnet and a Hall element (or
2 5 pick-up coil) in positions along a rotating axis of the
rotor and opposite to the rotating axis, respectively.
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In a motor mode, where the alternator 1 acts as a
synchronous motor, rotating magnetic field decision means,
or an ACG/ECU 3, which causes the stator 1S to generate a
rotating magnetic field, communicates with the engine ECU 4
to receive data such as an engine speed Ne, a battery
voltage Eb, an electrical load a, and the like . Upon
receipt of such data, the ACG/ECU 3 decides a speed of the
rotating magnetic field in the stator 1S (equal to a
rotating speed NO of the rotor) , a frequency f and a voltage
1 0 V of the direct current supplied to the stator coils 12
( i , a . , amplitude of the rotating magnetic field) , a phase
angle ~ of the rotating magnetic field to the
direct-current magnetic field of the rotor 1R, and the
like, all required for generation of a torque desirable to
1 5 assist or suppress the rotation of the engine, based on the
received data in a manner described later. Then, the
ACG/ECU 3 notifies a rotating magnetic field generator 8 of
the decided factors.
In the motor mode, the rotating magnetic field
2 0 generator 8 controls the amplitude and frequency of the AC
current supplied to the respective field coils 12a, 12b and
12c of the stator 1S, based on the data from the ACG/ECU 3
such as the speed (RPM) and the phase angle of the rotating
magnetic field, to generate a desired rotating magnetic
2 5 field in a manner described later. A switching controller
5 controls a switch circuit 6 in accordance with
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instructions separately input from the ACG/ECU 3 such that
the respective coils 12a, 12b and 12c of the stator 1S are
connected, as shown, to respective input contacts G of the
output controller 7 in the generator mode, and to
respective output contacts M of the rotating magnetic field
generator 8 in the motor mode .
When the rotor 1R generating a direct-current
magnetic field is rotated in proportion to the rotation
speed of the engine (not shown) , an alternating-current
1 0 electromotive force is induced in each of the stator coils
12 . In the generator mode that requires power generation
by the alternator 1, since the stator coils 12 are connected
to the output controller 7 through the respective contacts
G of the switch circuit 6, the alternating current
1 5 generated in the stator coils is converted into direct
current in the output controller 7 for supply to the battery
9 and an electrical load 30.
On the other hand, in the motor mode, the rotor coil
11 remains supplied with the direct current in the same
2 0 manner as in the generator mode, while the stator coils 12
are switched to the output contacts M and supplied with
alternating current at a proper frequency from the rotating
magnetic field generator 8. This causes a rotating
magnetic field in the stator 1S to allow the alternator 1 to
2 5 act as a synchronous motor.
When the battery 9 is in a predetermined charged
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state (e . g. , a full charged state or a charged state a
little less than the full charged state in view of
overcharge) and power generation by the alternator 1 is no
longer necessary, the switching controller 5 is notified
from the ACG/ECU 3 to switch over the connection from the
contacts G to those M so as to connect the stator coils 12 to
the rotating magnetic field generator 8 . At this time, if
the rotor coil 11 is subjected to self-magnetization as
shown by the dotted line 2A, it should be noted that it must
1 0 be switched to be magnetized by the battery 9. Such a
switching circuit is obvious to those skilled in the art,
and is not shown here for avoiding complication of the
drawing.
The rotating magnetic field generator 8 supplies the
1 5 AC current to the stator coils 12 at such a frequency f as to
induce in the stator 1S a rotating magnetic field with a
rotating speed equal to the rotating speed NO of the rotor
1R, thereby actuating the alternator 1 in the motor mode .
Thus, the alternator 1 operates as a synchronous motor and
2 0 rotate at the rotating speed NO in such a direction that the
rotation of the rotor 1R assists the engine torque. In this
case, if the phase angle of the rotor 1R with respect to the
phase of the rotating magnetic field in the stator 1S is so
set that the torque generated by the alternator 1 in the
2 5 motor mode compensates for the rotation loss due to the belt
driving torque and cooling fan resistance, it is possible
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to substantially cancel the rotation loss, and hence
improve engine efficiency. The magnitude and frequency of
the excitation voltage and the phase angle are decided in a
manner described later.
Fig. 3 is a flowchart showing the control process
according to an embodiment of the present invention. In
step 531, a voltage Eb at the terminal of the battery 9 is
measured. The measured battery voltage Eb is compared with
a reference voltage Eref (e.g., 13.5 volts) in step 532. If
1 0 the battery voltage Eb exceeds the reference voltage Vref,
the battery is judged being charged enough to eliminate
power generation by the alternator l, and the procedure
advances to step 533. If the battery voltage Eb is equal to
or less than the reference voltage Vref, this process is
halted.
In step 533, an engine speed Ne measured by the
rotating speed measurement part 41 of the ECU 4 is read, and
a current rotating speed NO of the rotor 1R is calculated on
the basis of the engine speed Ne and a pulley ratio which is
2 0 known. In step 534, a frequency f of excitation current to
be supplied to the stator coils 12 is calculated from the
equation:
f = P ~ NO/120,
where P is the Pole number of the stator coils 12, so
2 5 that a rotating magnetic field with the rotating speed NO is
induced in the stator 1S, and hence the alternator 1 is
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actuated as a synchronous motor. Thus, the rotating
magnetic field generator 8 generates alternating current at
the frequency thus calculated. Further, in step 534, a
target phase angle ~ 0 necessary to generate a desired
strength of torque is calculated accordingly from an
equation described later.
As well known, a torque T generated by the
alternator 1 in the synchronous motor mode is a function of
phase angle (phase shift angle) of the rotating magnetic
1 0 field in the stator 1S to a direct-current magnetic field of
the rotor coil 11, and magnitude of excitation voltage
and/or current, which is represented by the equation:
T = (V/k ~ NO) sin ~ ,
where V is a voltage of the excitation current and k
1 5 is a constant . When the rotating magnetic field shows a
leading phase to the direct-current magnetic field ( i . a . ,
the phase angle is positive) , such a torque as to assist the
rotation of the engine is generated; while when it is a
lagging phase ( i . a . , the phase angle is negative ) , such a
2 o torque as to suppress the rotation of the engine is
generated. In the embodiment of Fig. 3, since the rotation
of the engine is to be assisted, the rotating magnetic field
must be in a leading phase . The magnitude of the target
phase angle ~ 0 is determined from the above relation by the
25 following equation,
0 = Arc Sin (k ~ T ~ NO/V) .
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In step 535, the phase angle ~ of the
direct-current magnetic field generated in the rotor 1R is
measured by the rotor phase-angle detection part 46, for
example, based on the output of the Hall element 14 and the
rotating speed NO of the rotor. In step 536, determination
is made as to whether the measured phase angle ~ becomes
equal to the target phase angle ~ 0 adapted to generation of
a desired torque. If the determination is affirmative, the
procedure advances to step S37 in which the switching
1 0 controller 5 is driven to switch over the stator coils 12a
to 12c onto the contact M side . This causes the stator 1S
to generate a rotating magnetic field at the rotating speed
NO and the target phase angle ~ 0 with respect to the
direct-current magnetic field of the rotor, and hence the
1 5 rotor produces a desired engine assisting torque.
According to the present embodiment, the alternator
1 produces the torque that compensates for and hence
cancels rotation loss due to belt diving torque and/or
cooling fan resistance, thereby improving efficiency of the
2 0 internal combustion engine .
Although in the above embodiment the charged amount
in the battery is represented by the voltage at the terminal
of the battery, other known techniques can be adopted
instead. For example, the detection of the charged amount
2 5 can be achieved based on the change in specific gravity of
electrolyte in the battery, or history information on
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charged and discharged amounts . In the case that the
history information on the charged and discharged amounts
is used for the detection, a current amount of charge can be
obtained by detecting the charging and discharging current
and accumulating the charged and discharged amounts
sequentially on the initial amount . Then, when the current
amount of charge thus calculated is comparable to the
initial amount of charge or the full charged amount, the
determination at step S32 is affirmative.
1 0 The alternator 1 can be set in the motor mode for
other needs than the time when power generation is
unnecessary. For example, it is effective in starting the
engine with energizing the cel-motor or starting motor. In
such a case, the alternator 1 helps the cel-motor with the
1 5 assisting torque. This makes it possible to achieve
miniaturization of the cel-motor, and start the engine
quickly and surely.
Fig. 4 is a flowchart showing the control process
according to another embodiment of the present invention,
2 0 in which the alternator is set in the motor mode when
starting the engine. In step 541, judgment is made as to
whether or not the cel-motor is energized. If energized,
the voltage Eb at the terminal of the battery 9 is measured
in step 542. Then, in step 543, the measured battery
voltage Eb is compared with the reference voltage Eref in
the same manner as in the step S32 in Fig. 3. When the
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battery voltage Eb exceeds the reference voltage Eref, the
procedure advances to step 544; when it is equal to or less
than the reference voltage Eref, this process is ended.
As is similar to the steps S33 through 37 in Fig. 3,
operations from steps S44 to S48 are executed one by one,
such as measurement of the engine speed Ne, calculation of
the current rotating speed NO of the rotor, calculation of
the frequency f of an excitation power source for the stator
coils and the target phase angle ~ 0, generation of
1 0 alternating current at the frequency f, measurement of the
rotor phase angle ~ , comparison of the rotor phase angle
b with the target phase angle d 0, and switching over the
stator coils 12 from the terminals G on the output
controller side to the contacts M on the side of the
1 5 rotating magnetic field generator 8. Steps S42 and S43 may
be omitted so that the engine will be assisted each time the
engine is started, regardless of the magnitude of the
battery voltage Eb.
Referring next to a flowchart of Fig. 5, still
2 0 another embodiment of the present invention will be
described. In this process, the alternator 1 is made
active as a motor so that the engine speed can be stabilized
during idling.
When an idling condition of the engine is detected
2 5 in step S51 in a proper manner known in the art, the engine
speed Ne is measured to calculate the rotating speed NO of
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the rotor in step 552. Then, in step 553, a deviation d N
of the engine speed Ne from a target idling speed Ntarg is
calculated. After that, operations from steps S54 to S57
are executed one by one, as is similar to the
above-mentioned steps S34 through 537, such as calculation
of the frequency f of the excitation power source for the
stator coils and the target phase angle ~ 0, generation of
alternating current at the frequency f, measurement of the
rotor phase angle ~ , comparison of the rotor phase angle
1 0 d with the target phase angle ~ 0, and switching over the
stator coils 12 from the contacts G on the output controller
side to the contacts M on the side of the rotating magnetic
field generator.
As discussed above, when the rotating magnetic field
1 5 generated in the stator 1S shows a leading phase to the
direct-current magnetic field of the rotor 1R ( i . a . , the
phase angle ~ is positive) , the alternator 1 in the motor
mode generates such a torque as to assist the rotation of
the engine; when it is a lagging phase ( i . a . , the phase
2 o angle ~ is negative) , it generates such a torque as to
suppress the rotation of the engine .
When the engine speed Ne is less than the target
rotating speed Ntarg and the deviation ~ N is negative, the
target phase angle ~ 0 is set to a positive value in step S54
2 5 so that the alternator 1 will generate a torque for
assisting the rotation of the engine. Conversely, when the
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engine speed Ne exceeds the target rotating speed Ntarg and
the deviation ~ N is positive, the target phase angle ~ 0 is
set to a negative value in step S54 so that the alternator 1
will generate a torque for suppressing the rotation of the
engine.
Referring next to a flowchart of Fig. 6, yet another
embodiment of the present invention will be described. In
this process, the alternator 1 is set in the motor mode to
assist the engine torque so as to improve acceleration
1 o performance.
In step S61, the acceleration judgment part 42 of
the engine ECU 4 judges whether or not the vehicle is
accelerating. The judgment is made, for example, based on
the increase rate of the vehicle speed or the throttle
1 5 position B th. If the vehicle is accelerating, a current
electrical load a is measured in step 562. Then, in step
563, judgment is made as to whether or not the electrical
load a is equal to or less than a reference value. If the
electrical load a exceeds the reference value, the process
2 0 is ended without applying any torque for assisting
acceleration because interruption of the power generation
is unfavorable. On the other hand, if the electrical load a
is equal to or less than the reference value, the
acceleration is assisted with a torque generated in the
2 5 rotor 1R through the following steps .
That is, operations from steps S64 to S68 are
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executed one by one, as is similar to steps S33 through S37
in Fig. 3, such as measurement of the engine speed Ne,
calculation of the rotating speed NO of the rotor,
calculation of the frequency f and the phase angle b 0 of
the excitation power source for the stator coils,
generation of alternating current at the frequency f,
measurement of the rotor phase angle d , comparison of the
rotor phase angle ~ with the target phase angle ~ 0, and
switching over the stator coils 12 from the terminals G on
1 0 the output controller side to the contacts M on the side of
the rotating magnetic field generator 8 . In this case, the
target phase angle ~ 0 is, of course, positive .
When the alternator 1 is operated in the motor mode,
the torque does not always assist the rotation of the engine
1 5 as in the above embodiments . For example, if such a torque
as to suppress the rotation of the engine is generated upon
braking operation of an engine brake, the alternator 1 acts
as a load to improve the braking performance . In such a
control process, the content of judgment in the above step
2 0 S61 of Fig. 6 has only to be changed to "being in a braking
condition or not", so that illustration and description of
the process are omitted here . Here, it should be noted that
the target phase angle ~ 0 is set negative for suppressing
the rotation of the engine .
2 5 The process of controlling the alternator 1 to
produce such a negative torque as to suppress the rotation
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of the engine can also be applied to traction control (TSC)
conventionally carried out when a wheel spin ( slipping
condition of drive wheels) of the vehicle is detected. As
can easily be found from the above description, this
control process requires only to change the content of
judgment of the above step S61 of Fig. 6 to "whether or not
traction control (TSC) is instructed".
Specifically, when the wheel spin detection part 44
of the engine ECU 4 detects the wheel spin, judgment is made
1 0 first as to whether or not traction control (TSC) is
instructed. If the judgment result is Yes, subsequent
steps S62 to S68 are executed. In this case, the target
phase angle ~ 0 is set negative too, and the value thereof
may be determined experientially and/or experimentally
1 5 according to the degree of the wheel spin. This makes it
possible to carry out traction control in quicker response
than that in such a conventional control system as to
decrease the engine torque by interrupting the fuel supply
or the like . The suppression of the engine torque
2 0 according to the present invention may be used together
with such a conventional control system as to decrease the
engine torque by interrupting the fuel supply or the like .
Fig. 7 is a flowchart showing the control process
according to yet another embodiment of the present
2 5 invention, in which when the engine speed is close to or
exceeds a maximum limit, the alternator 1 is switched into
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the motor mode to generate such a suppressing torque as to
reduce the rotation of the engine, whereby over revolution
of the engine is prevented.
The engine speed Ne is measured in step 591, and the
5 measured engine speed Ne is compared with a maximum engine
speed Nmax in step 592. If it is judged that the engine
speed Ne reaches the maximum engine speed Nmax, a rotating
speed NO of the rotor at that time is calculated as a
function of the engine speed Ne . After that, operations
1 0 from steps S94 to S97 are executed one by one, as is similar
to the above steps S34 through 537, such as calculation of
the frequency f and the phase angle ~ 0 of the excitation
power source for the stator coils, generation of
alternating current at the frequency f, measurement of the
1 5 rotor phase angle ~ , comparison of the rotor phase angle
with the target phase angle ~ 0, and switching over the
stator coils 12 from the terminals G on the output
controller side to the contacts M on the side of the
rotating magnetic field generator 8. In this case, the
2 0 target phase angle ~ 0 is, of course, negative . On the
other hand, if the judgment result at step S92 is No, the
above operations S93-S97 are not executed.
Fig. 8 is a flowchart showing the control process
according to yet another embodiment of the present
2 5 invention, in which when the crusing speed of the vehicle or
the like with the internal combustion engine mounted
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thereon is close to or exceeds a maximum limit, the
alternator 1 is switched into the motor mode to generate
such a suppressing torque as to reduce the rotation of the
engine, whereby a vehicle speed limiting function is
realized.
In step 5101, the vehicle speed measurement part 45
of the ECU 4 measures a current vehicle speed Vs . The
measured vehicle speed Vs is compared with a maximum speed
Vmax in step S102. If it is judged that the vehicle speed
1 0 Vs reaches or is over the maximum speed Vmax, then
operations from steps 5103 to 5106 are executed one by one,
as is similar to the above steps S34 through 537, such as
calculation of the frequency f and the target phase angle
0 of the excitation power source for the stator coils,
1 5 generation of alternating current at the frequency f,
measurement of the rotor phase angle ~ , comparison of the
rotor phase angle c5 with the target phase angle d 0, and
switching over the stator coils 12 from the terminals G on
the output controller side to the contacts M on the side of
2 0 the rotating magnetic field generator 8 . In this case, the
target phase angle d 0 is, of course, negative . On the
other hand, if the judgment result at step 5102 is No, the
above operations 5103 - 5106 are not executed.
In the above embodiments, although a step of
2 5 determining a battery voltage or electrical load is not
included in some cases, such a determination step may be
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adopted in said cares . In the case such a step is adopted,
the switching into the motor mode may be inhibited when the
battery voltage is equal to or less than a predetermined
reference value, or when the electric load exceeds a
predetermined reference value. Further, if the magnitude
of such a torque as to assist or suppress the engine reaches
a target value at the beginning of switching the contacts
from the G side to the M side, it may disturb the engine . It
is therefore desirable to control the torque such that the
1 0 amplitude of alternating current to be supplied to the
stator coils 12 is small enough to set the generated torque
to substantial zero or small enough just after the
switching action, and thereafter increases gradually with
time. Furthermore, in the above embodiments, the
1 5 alternator includes a stator with three-phase windings, but
the present invention is not limited thereto, and any other
multi-phase windings such as of four-phase or five-phase
can be adopted instead.
Industrial Applicability
2 0 The following advantages are achieved by the present
invention.
(1) Conventionally used or existing alternators of
direct-current magnetization type or permanent magnet type
can also be operated as a synchronous motor to generate such
2 5 a torque as to assist or suppress the rotation of the
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engine.
(2) Generation of such a torque as to compensate
for variation in rotation of an internal combustion engine
reduces the fluctuation in engine speed during the idling
of the engine, resulting in stable engine operation.
(3) If the torque assisting the rotation of the
internal combustion engine is generated when power
generation by the alternator is no longer necessary, it is
possible to cancel rotation loss due to belt driving torque
1 0 and cooling fan resistance, and hence improve engine
efficiency.
( 4 ) When the torque assisting the rotation of the
internal combustion engine is generated at the time of
starting the internal combustion engine, it is possible to
1 5 help the cel-motor with such an assisting torque, and hence
to start the engine quickly and surely, and furthermore to
realize the miniaturization of the cel-motor.
(5) When the torque assisting the rotation of the
internal combustion engine is generated in an acceleration
2 0 condition of the vehicle, it is possible to improve
acceleration performance.
(6) When the torque suppressing the rotation of the
internal combustion engine is generated in a braking
condition of the vehicle, it is possible to improve braking
25 performance.
(7) If the torque suppressing the rotation of the
CA 02252842 1998-10-19
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internal combustion engine is generated when the wheel spin
of the vehicle is detected, it is possible to improve
responsive performance of the traction control.
(8) If the torque suppressing the rotation of the
internal combustion engine is generated when the rotating
speed of the internal combustion engine or the speed of the
vehicle and the like with the internal combustion engine
mounted thereon, is likely to exceed a maximum limit, it is
possible to prevent over revolution of the internal
1 0 combustion engine, or overspeed of the vehicle .
